Muscle contraction gluconeogenesis

Skeletal muscle is specialized to perform intermittent mechanical work. As described previously, the energy sources that provide ATP for muscle contraction depend on the degree of muscular activity and the physical status of the individual. During fasting and prolonged starvation, some skeletal muscle protein is degraded to provide amino acids (e.g., alanine) to the liver for gluconeogenesis. 

Its cellular functions comprise skeletal and cardiac muscle contraction cellular secretion exocrine, endocrine, and neurotransmitters, neural excitation and regulation of membrane ion transport enzyme regulation (gluconeogenesis and glycogenolysis) and cell growth and division. 

Substrate cycling also provides a means of increasing the sensitivity and speed of metabolic regulation. The increased rate of glycolysis in response to a need for ATP for muscle contraction would imply a more or less instantaneous 1000-fold increase in phosphofructokinase activity if phosphofructokinase were inactive and fructose 1,6-bisphosphatase active. If there is moderate activity of phosphofructokinase, but greater activity of fructose 1,6-bisphosphatase, so that the metabolic flux is in the direction of gluconeogenesis, then a more modest increase in phosphofructokinase activity and decrease in fructose 1,6-bisphosphatase activity will achieve the same reversal of the direction of flux. 

Skeletal muscle utilizes glucose as a fuel, forming both lactate and CO2. It stores glycogen as a fuel for its use in muscular contraction and synthesizes muscle protein from plasma amino acids. Muscle accounts for approximately 50% of body mass and consequently represents a considerable store of protein that can be drawn upon to supply amino acids for gluconeogenesis in starvation. 

Contract sphincters of GI tract. Increases lipolysis in adipose tissue, increases anabolism in skeletal muscle, increase glycogenolysis and gluconeogenesis. 

Epi > NE Iso Phenylephrine Prazosin Vascular smooth muscle GU smooth muscle Liver Intestinal smooth muscle Heart Contraction Contraction Glycogenoly sis gluconeogenesis Hyperpolarization and relaxation Increased contractile force arrhythmias... 

Chemistry, mechanism, and effects Glucagon is the product of the A cells of the endocrine pancreas. Like insulin, glucagon is a peptide but unlike insulin, glucagon acts on G protein-coupled receptors. Activation of glucagon receptors, which are located in heart, smooth muscle, and liver, stimulates adenylyl cyclase and increases intracellular cAMP. This results in increases in the heart rate and the force of contraction, increased hepatic glycogenolysis and gluconeogenesis and relaxation of smooth muscle. The smooth muscle effect is particularly marked in the gut. 

In a differentiated organism, each tissue must be provided with fuels that it can utilize for its own energy needs to perform its function. For example, muscles need to generate adenosine triphosphate (ATP) for their mechanical work of contraction, and the liver needs ATP for the synthesis of plasma proteins and fatty acids, gluconeogenesis, or for the production of urea for the excretion of nitrogenous compounds. 

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